Mountain House on the Hundwiler Höhe, Switzerland

For over 100 years a house has stood on this site on a hilltop 1,300 m above sea level in the canton of Appenzell. The present development reflects the traditional compact form of many houses in this cool, sunny region, where the fenestration is oriented to the morning sun. There is no road access to the house. The highly insulated outer wall units in timber panel construction were, therefore, brought to the site by helicopter and erected within 12 hours. The house has a system of transparently insulated sandlime brick walls that store heat during the day and give it off internally in the evening. After sunny days, this system obviates the need for any other form of heating. The external cladding to these walls consists of an outer layer of glass and an internal layer of dark fibre-cement sheets, with transparent insulation between. The insulation is in the form of narrow, open plastic tubes that allow sunlight to enter, but prevent the heat gained from escaping outwards. The dark-coloured sheets heat up to about 90 °C on cold, sunny days, and the external face of the brickwork beyond to approximately 75 °C. This heat penetrates to the inner face of the wall, which reaches a temperature of up to 30 °C in the evening and acts as a large-area radiating panel. During overcast periods, a special stove and a wood-burning kitchen range in a central position heat all the living areas. The projecting eaves help to ensure that the rooms are not overheated in summer.